Human Monocyte-Derived Macrophages Express an [nearly =] 120-kD Ox-LDL Binding Protein With Strong Identity to CD68

• Published in: Arteriosclerosis, thrombosis, and vascular biology Vol. 17; no. 11; pp. 3107 - 3116
• Main Authors: van der Kooij, Maaike A, von der Mark, Elisabeth M, Kruijt, J. Kar, van Velzen, Agnes, van Berkel, Theo J.C, Morand, Olivier H
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Heart Association, Inc 01.11.1997; Hagerstown, MD Lippincott
• Subjects: Atherosclerosis (general aspects, experimental research); Biological and medical sciences; Blood and lymphatic vessels; Cardiology. Vascular system; Medical sciences; Vascular disease; Human; Lipoprotein LDL; Cell culture; Pathogenesis; Atherosclerosis; Cardiovascular disease; Oxidation; Macrophage
• ISSN: 1079-5642; 1524-4636
• DOI: 10.1161/01.ATV.17.11.3107

A protein that specifically binds oxidized LDL (Ox-LDL) has recently been characterized in mouse peritoneal macrophages and identified as macrosialin, a protein with a molecular weight of 95 kD. First, the present work shows that human monocyte-derived macrophages express a membrane protein with a molecular weight of [nearly =] 120 kD that selectively binds Ox-LDL. Second, we tested whether this [nearly =] 120-kD Ox-LDL binding protein had any relation to CD68, the human homologue of macrosialin. The following evidence was obtained to support the role of CD68 as an Ox-LDL binding protein(1) Ligand blots with Ox-LDL and Western blots with Ki-M6, an anti-human CD68 monoclonal antibody, revealed a single band with a molecular weight of [nearly =] 120 kD under reducing and nonreducing condition. (2) The expression patterns of the [nearly =] 120-kD Ox-LDL binding membrane protein and of CD68 paralleled each other during monocyte/macrophage differentiation. (3) Digestion with N-glycosidase F demonstrated that both CD68 and the Ox-LDL binding protein are glycoproteins; both showed a similar shift of [nearly =] 18 kD in apparent molecular weight. (4) CD68, probed with monoclonal antibody Ki-M6, and the [nearly =] 120-kD Ox-LDL binding protein were coprecipitated with EBM11, another anti-CD68 antibody. About 5000 molecules of CD68 are expressed on the cell surface of human macrophages. Ligation of I-Ki-M6 to cells leads to its internalization and degradation. This capacity would be sufficient to allow for the specific uptake and degradation of Ox-LDL. Taken together, these data support a role for CD68 as a specific Ox-LDL binding protein in human monocyte-derived macrophages. (Arterioscler Thromb Vasc Biol. 1997;17:3107-3116.)